Robotic light touch assists human balance control during maximum forward reaching
ObjectiveWe investigated how light interpersonal touch (IPT) provided by a robotic system supports human individuals performing a challenging balance task compared to IPT provided by a human partner. BackgroundIPT augments the control of body balance in contact receivers without a provision of mechanical body weight support. The nature of the processes governing the social haptic interaction, whether they are predominantly reactive or predictive, is uncertain. MethodTen healthy adult individuals performed maximum forward reaching (MFR) without visual feedback while standing upright. We evaluated their control of reaching behaviour and of body balance during IPT provided by either another human individual or by a robotic system in two alternative control modes (reactive vs predictive). ResultsChanges in reaching behaviour under the robotic IPT, such as lower speed and straighter direction were linked to reduced body sway. MFR of the contact receiver was influenced by the robotic control mode such as that a predictive mode reduced movement variability and increased postural stability to a greater extend in comparison to human IPT. The effects of the reactive robotic system, however, more closely resembled the effects of IPT provided by human contact provider. ConclusionThe robotic IPT system was as supportive as human IPT. Robotic IPT seemed to afford more specific adjustments, such as trading reduced speed for increased accuracy, to meet the intrinsic demands and constraints of the robotic system. Possibly, IPT provided by a human contact provider reflected reactive interpersonal postural coordination more similar to the robotic systems follower mode. PrecisInterpersonal touch support by a robotic system was evaluated against support provided a human partner during maximum forward reaching. Human contact receivers showed comparable benefits in their reaching postural performance between the support conditions. Coordination with the robotic system, nevertheless, afforded specific adaptations in the reaching behaviour.